CN111285982B - Chiral supramolecular azobenzene assembly and in-situ construction method - Google Patents

Chiral supramolecular azobenzene assembly and in-situ construction method Download PDF

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CN111285982B
CN111285982B CN202010121546.8A CN202010121546A CN111285982B CN 111285982 B CN111285982 B CN 111285982B CN 202010121546 A CN202010121546 A CN 202010121546A CN 111285982 B CN111285982 B CN 111285982B
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azobenzene
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CN111285982A (en
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张伟
程笑笑
缪腾飞
马浩天
周年琛
张正彪
朱秀林
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Suzhou University
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Abstract

The invention discloses a chiral supramolecular azobenzene assembly and an in-situ construction method. The method comprises the following steps: chiral azobenzene monomer, macromolecular chain transfer agent, free radical initiator, alcohol solvent and water are mixed and subjected to polymerization reaction in an oxygen-free environment to obtain supramolecular chiral azobenzene polymer.

Description

Chiral supramolecular azobenzene assembly and in-situ construction method
Technical Field
The invention belongs to the technical field of polymer synthesis, and particularly relates to synthesis of chiral azobenzene molecules and polymerization-induced chiral self-assembly.
Background
Chirality refers to the property of an object not coinciding with its mirror image. It is a basic attribute in nature and widely exists in nature, including micro-sized chiral small molecules, biomacromolecules, animal and plant helical structures on a macro scale, interstellar vortexes and the like. Scientists construct a precise and ordered chiral spiral structure by a supermolecule assembly method, simulate interesting phenomena in life, and prepare chiral materials, asymmetric catalytic materials, bionics materials and the like. After the first introduction of the concept of "supramolecules" by french scientist Lehn in 1978, researchers have conducted extensive studies on supramolecular chirality. The supermolecule is an aggregate which is formed by combining two or more molecules together by virtue of intermolecular non-covalent bond interaction, has a complex ordered structure, keeps certain integrity and has a definite microstructure and macroscopic characteristics. The azobenzene compound and the derivative thereof are one of the common photoresponse materials in daily production and life, and the unique reversible photocis-trans isomerization performance of the azobenzene compound can generally cause the physical and chemical properties of the azobenzene compound to be obviously changed, so that the properties of the azobenzene compound are obviously changed. The azobenzene compound has N = N double bonds in the structure, lone pair electrons on the N = N double bonds can generate pi-pi and N-pi electron transition when being excited by light irradiation, and therefore cis-trans photoisomerization can be generated under the light irradiation condition. During the photo-isomerisation process, two isomeric forms are produced, a more stable trans isomer and a more active cis isomer. The relatively planar trans-isomer can be converted into a curved cis-structure under ultraviolet radiation, the cis-isomer is more active than the trans-isomer, the cis-isomer can be converted into the trans-isomer under relatively mild conditions, and the reversible conversion process can cause the structure and the performance of the material to be changed. In the prior art, a research group successfully realizes the construction of the supermolecule chirality of side-chain type and main-chain type achiral azobenzene polymers through chiral solvation induction, and the supermolecule chirality of the side-chain azobenzene polymers is derived from the supermolecule structure of a relatively planar trans-azobenzene unit in a polymer structure.
Disclosure of Invention
Aiming at the situation, the invention designs that a solvophilic macromolecular chain transfer agent is synthesized by thermal polymerization, then the synthesized macromolecular chain transfer agent is utilized to successfully initiate a solvophobic chiral azobenzene monomer to be polymerized in ethanol/water by a thermal initiator, and self-assembly is carried out in the polymerization process to construct an assembly containing the supermolecule chirality of azobenzene.
In order to achieve the purpose, the invention prepares the block copolymer in situ, and provides a new method for an azobenzene supermolecule chiral assembly with a spiral fiber shape: polymerization induces chiral self-assembly. The specific technical scheme is as follows:
the preparation method of the chiral supramolecular azobenzene assembly comprises the following steps of mixing a chiral azobenzene monomer, a macromolecular chain transfer agent, a free radical initiator, an alcohol solvent and water, and carrying out polymerization reaction in an anaerobic environment to obtain the supramolecular chiral azobenzene assembly.
In the invention, the chemical structural formula of the chiral azobenzene monomer is as follows:
Figure 189750DEST_PATH_IMAGE001
Figure 294104DEST_PATH_IMAGE002
the chiral azobenzene monomer isS-an azobenzene monomer,RAn azobenzene monomer, a being 1 to 9 and b being 1 to 12.
In the invention, the alcohol solvent is any one of methanol, ethanol, propanol and butanol, and ethanol is preferred.
In the invention, the polymerization reaction is carried out at 60-80 ℃ for 12-18 hours, preferably at 70 ℃ for 15 hours.
According to the invention, the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent is 12-18: 1; preferably, the amount of free radical initiator is 20% of the molar amount of macromolecular chain transfer agent.
According to the method, methacryloyl chloride and an intermediate product 4 are used as raw materials, and reflux reaction is carried out under inert gas to prepare a chiral azobenzene monomer; intermediate 4 is as follows:
Figure 233241DEST_PATH_IMAGE003
preferably, p-nitrophenol and chiral alcohol are used as raw materials to prepare an intermediate product 1; the intermediate product 1 is subjected to amination and diazotization in sequence and then reacts with phenol to obtain an intermediate product 3; intermediate 3 is reacted with a halogen alcohol to provide intermediate 4. To be provided withRThe reaction described above can be schematically represented as follows, for example by azobenzene:
Figure 619092DEST_PATH_IMAGE004
specific reaction steps can be exemplified as follows:
to synthesizeRAn azobenzene monomer is exemplified. The raw materials of p-nitrophenol and chiral octanol (A), (B)S-octanol), diisopropyl azodicarboxylate and diethyl ether were added to a three-necked flask, and triphenylphosphine was added to the flask; reacting for 12 hours at room temperature; after the reaction is finished, carrying out suction filtration, then spin-drying the solvent, and then carrying out column chromatography purification and drying to obtain an intermediate product 1; adding the intermediate product 1 into a three-neck flask, adding tin dichloride, heating for reaction for 3 hours, adding into ice water after the reaction is finished, adjusting the pH value to 7-8, extracting with ethyl acetate, spin-drying the solvent, purifying by column chromatography, and drying to obtain an intermediate product 2; diluting hydrochloric acid with water, dropwise adding the diluted hydrochloric acid into the intermediate product 2 under stirring, and dropwise adding a sodium nitrite aqueous solution after the dropwise addition is finished, so as to obtain a diazonium salt solution of the intermediate product 2; dropwise adding the diazonium salt solution of the intermediate product 2 into a solution containing phenol, sodium hydroxide and sodium bicarbonate under the condition of mechanical stirring, reacting for 4 hours after dropwise adding is finished to obtain a yellowish-brown turbid liquid, and finally obtaining a yellow intermediate product 3 after carrying out suction filtration, extraction, drying, column chromatography purification and vacuum drying on the obtained turbid liquid; potassium carbonate, intermediate 3, potassium iodide and 6-chlorohexanol were mixed and heated to 85 deg.f o C, reacting for 4 hours, cooling to room temperature, extracting with ethyl acetate and water, drying the obtained oil phase with anhydrous sodium sulfate, performing rotary evaporation, purifying with column chromatography, and drying to obtain an intermediate product 4; adding triethylamine, methacryloyl chloride and an intermediate product 4 into tetrahydrofuran, performing reflux reaction for 24 hours under argon, and adding ammonium chloride NH 4 Aqueous Cl solution, followed by extraction with dichloromethane, the combined organic extracts washed with water, dried over anhydrous sodium sulfate, and the crude product purified by flash chromatography to give a yellow solid after dryingR-an azobenzene monomer.S-a step of synthesis of azobenzene monomer andRthe azobenzene monomer is the same except in stepR-the use of octanol.
In the invention, a hydrophilic monomer and a micromolecular chain transfer agent are used as raw materials to prepare a macromolecular chain transfer agent; preferably, a hydrophilic monomer, a micromolecular chain transfer agent, a free radical initiator and ethanol are added into a reaction container, and then the mixture is stirred for 4-8 hours at the temperature of 70-80 ℃; stopping the reaction, then settling in n-hexane for 3 times, dialyzing in a dialysis bag for three days, settling in n-hexane after dialysis, and then drying to obtain the solvophilic macromolecular chain transfer agent; further preferably, the molar ratio of the hydrophilic monomer, the small molecule chain transfer agent and the radical initiator is 50 to 500: 1: 0.2, preferably 60: 1: 0.2. For example, the chemical structure of the macromolecular chain transfer agent is as follows:
Figure 225653DEST_PATH_IMAGE005
according to the invention, the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent is 12-18: 1, preferably 15: 1; the amount of water is 0-90% of the total volume of the alcohol solvent and water and is not 0, such as 4-20%.
Further, the original reaction material chiral alcohol of the invention is selected from any one of chiral octanol, chiral hexanol and chiral butanol, preferably chiral octanol; the halogen alcohol is selected from any one of 6-chlorohexanol, 12-bromo-1-dodecanol, 8-bromo-1-heptanol, 4-bromobutanol and 2-bromoethanol, preferably 6-chlorohexanol; the catalyst used in the reaction of methacryloyl chloride and intermediate 4 is selected from any one of sodium hydroxide, triethylamine, sodium bicarbonate and potassium carbonate, preferably triethylamine; the solvent for the reaction of methacryloyl chloride and intermediate 4 is selected from tetrahydrofuran, acetone, dichloromethane and n-hexane, preferably Tetrahydrofuran (THF); the radical initiator is selected from any one of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate and 4,4 '-azo (4-cyanovaleric acid), preferably 4,4' -azo (4-cyanovaleric acid) (ACVA).
Further, the hydrophilic monomer of the present invention is selected from any one of methacrylic acid, acrylic acid, 4-vinylpyridine, and N-isopropylacrylamide, preferably methacrylic acid (MAA); the small molecule chain transfer agent is selected from any one of 4-cyano-4- (thiobenzoyl) valeric acid, 2-methyl-2- (dodecyl trithiocarbonate) propionic acid, 4-cyano-4- ((((ethylthio) carbonylthio) thio) valeric acid, 4-cyano-4- [ [ (dodecylthio) thiolmethyl ] thio ] valeric acid, and preferably 4-cyano-4- (thiobenzoyl) valeric acid (CPADB).
In the invention, the oxygen-free environment is inert gas. The inert gas in the invention is selected from any one of argon, nitrogen, helium and neon, and argon is preferred.
In the preparation method disclosed in the present invention, after completion of each reaction step, purification steps such as chromatography, dissolution/precipitation separation, filtration and the like may be performed in order to obtain a product with higher purity.
Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:
the invention constructs the spiral nanofiber assembly in the mixed solution of water and ethanol for the first time. In recent years, azobenzene polymers play an important role in scientific research and industrial production due to structural particularity, and chiral azobenzene polymer materials have important roles in the research of chiral resolution, enantiomer crystallization and optical switch materials as a class of high polymer materials with special performance. The process provided by the invention is used as a strategy for effectively constructing the controllable and various-shape azobenzene polymer supramolecular chiral assembly, and a synthetic method of a chiral material is expanded.
Drawings
FIG. 1 is a nuclear magnetic diagram of a chiral monomer in example 1. The nuclear magnetic peak corresponds to the monomer, and no impurity peak indicates that the monomer is relatively pure.
FIG. 2 is a nuclear magnetic spectrum and GPC elution curve of the macromolecular chain transfer agent of example 2. Wherein FIG. 2A is a nuclear magnetic diagram of the macromolecular chain transfer agent; wherein a post-modified benzyl group is used for GPC testing. FIGS. 2B and 2C are post-modified nuclear magnetic maps and GPC outflow curves.
FIG. 3 shows the NMR trace (A) and the conversion (B) in example 3.
FIG. 4 is PMAA 51 -S 15 And PMAA 51 -R 15 CD diagram of block copolymer assembly in water/ethanol mixed system andg CD figure (a). Wherein the percentage of water in the total volume is 4%, 10% and 20%. The A diagram is CD and ultraviolet spectrum diagram of different water content, and the B diagram is CD and ultraviolet spectrum diagram of different water contentg CD And (4) a spectrogram. Whereing CD Is calculated as [ ellipticity/32,980]Absorbance. The volume of water is different, the CD of the block is fixed andg CD the values are different.
FIG. 5 is PMAA 51 -S 15 And PMAA 51 -R 15 TEM image of block copolymer assembly in water/ethanol mixed system. Wherein the percentage of water in the total volume is A graph, D graph 4%, B graph, E graph 10%, C graph and F graph 20%. The morphology of the fixed block is different when the volume of water is different. When the percentage of water is 4%, obtaining the long fibrous morphology of the A picture and the D picture; the fiber has a length of several micrometers and a width of 20-100 nanometers.
FIG. 6 is PMAA 51 -S 15 And PMAA 51 -R 15 AFM images of block copolymer assemblies in a 4% water/ethanol mixed system. Wherein the percentage of water in the total volume is 4 percent, and long fibrous morphology is obtained; the AFM images are characterized by a helical fiber morphology.
Detailed Description
The preparation method of the chiral supramolecular azobenzene assembly comprises the following steps of mixing a chiral azobenzene monomer, a macromolecular chain transfer agent, a free radical initiator, an alcohol solvent and water, carrying out polymerization reaction in an oxygen-free environment to obtain a supramolecular chiral azobenzene polymer, and carrying out in-situ preparation on an azobenzene block copolymer assembly.
The invention will be further described with reference to specific embodiments and drawings.
Chemical reagents:
4-cyano-4- (thiobenzoyl) pentanoic acid, 97%, aladin;
4,4' -azo (4-cyanovaleric acid), 98%, J & K Chemical; recrystallizing twice before use;
6-chlorohexanol, 95%, Acros;
95% of p-nitrophenol and Aladdin;
phenol, AR, aladin;
tin dichloride, 98%, Energy Chemical;
diisopropyl azodicarboxylate, 98%, 3A Chemicals;
triphenylphosphine, 99%, great;
99% of benzyl chloride, Macklin;
99% of methacrylic acid, and aladin;
chiral octanol (R-an octanol group,S-octanol), 99%, TCI;
tetrahydrofuran, 99.5%, Nanjing chemical reagents, Inc.;
ethanol, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
methacryloyl chloride, 95%, aladin;
hydrochloric acid, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
sodium nitrite, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
potassium iodide, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
triethylamine, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
anhydrous sodium sulfate, 98%, national drug group chemical reagents ltd;
potassium carbonate; analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
sodium hydroxide; analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
sodium bicarbonate; analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
ethyl acetate, 99.5%, Jiangsu Qiangsheng functional chemistry GmbH;
petroleum ether, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
diethyl ether, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
ammonium chloride, analytically pure, Jiangsu Qiangsheng functional chemistry GmbH;
testing instruments and conditions:
gel Permeation Chromatography (GPC): molecular weight and molecular weight distribution Using a gel permeation chromatograph with TOSOH TSKgel SuperHM-M, which is an automatic feeding model, polymethyl methacrylate (PMMA) was used as a standard to calculate the molecular weight of the polymer, N, N-Dimethylformamide (DMF) was used as a mobile phase at a flow rate of 0.65 mL/min and a temperature of 40 deg.C o C。
Nuclear magnetic resonance hydrogen spectrum ( 1 H-NMR): using a Bruker 300MHz NMR spectrometer in CDCl 3 And DMSO-d 6 As solvent, TMS as internal standard, measured at room temperature.
Transmission Electron Microscope (TEM): the accelerating voltage was 120 kV using a HITACHI HT 7700 transmission electron microscope.
Atomic Force Microscope (AFM) A Bruker Multimode 8 atomic force microscope was used, and the imaging mode was tapping.
Circular Dichroism (CD): using a Japanese JASCO J-815 circular dichroism spectrometer, 25 o And C, measuring, wherein the scanning speed is 200 nm/min, the scanning range is 300-600 nm, and the bandwidth is 2 nm.
Ultraviolet visible spectrum (UV-vis): and (3) using a Shimadzu UV-2600 ultraviolet spectrometer, wherein the scanning range is 300-600 nm.
Differential Scanning Calorimeter (DSC): using TA DSC 250, the temperature ramp rate was 10 o C/min。
Small angle X-ray scattering (SAXS): an Anton Paar SAXSess MC2 diffractometer, Cu Ka radiation source, wavelength 0.154 nm was used.
Polarizing microscope (POM): a CNOPTEC BK-POL polarizing microscope was used.
Example 1: single synthetic chiralityAzobenzene monomer (C)S-azobenzene andR-azobenzene)
To synthesizeSAzobenzene is an example. 13.9 g of p-nitrophenol serving as a raw material and 0.1 mol of the p-nitrophenol,ROctanol (13.0 g, 0.1 mol), diisopropyl azodicarboxylate (20 mL) and 300 mL diethyl ether were added to a three-necked flask, and triphenylphosphine (26.2 g, 0.1 mol) was dissolved in 50mL diethyl ether at 0 ℃ and then added to the flask. Reacting for 12 hours at room temperature; after the reaction is finished, suction filtration is carried out, then the solvent is dried in a spinning mode, and then column chromatography purification and drying are carried out. Intermediate 1 (21.2 g, 0.084 mol) was obtained.
Intermediate 1 (21.2 g, 0.084 mol) and 100 mL of ethanol were added to a three-necked flask, followed by addition of tin dichloride (31.8 g, 0.17 mol), and heating to 70 o C, reacting for 3 hours. After the reaction, the reaction mixture was poured directly into 600 mL of ice water, and potassium carbonate was added to adjust the pH to 7. Extracting with ethyl acetate, drying with anhydrous sodium sulfate, vacuum filtering, spin drying solvent, purifying by column chromatography, and drying. Intermediate 2 (16.2 g, 0.073 mol) was obtained.
At low temperature 0 o Under C, sodium nitrite (7.0 g, 0.11 mol) was dissolved in 100 mL of water, 30 mL of hydrochloric acid was diluted with 30 mL of water, and the diluted hydrochloric acid was added to intermediate 2 (16.2 g, 0.073 mol) with stirring over 30 minutes. After the above steps are completed, the aqueous solution of sodium nitrite is added dropwise (the dropwise adding time is 20 minutes) into the hydrochloride solution, and the temperature is always kept at 0 o C, thereby obtaining a diazonium salt solution of intermediate 2.
Phenol (16.0 g) was dissolved in 400 mL of water at 0 deg.C, and sodium hydroxide NaOH (8.0 g) and sodium bicarbonate NaHCO were added 3 (8.4 g). The diazonium salt solution of intermediate 2 obtained previously was then added dropwise to the above-mentioned phenol solution under mechanical stirring, maintaining the conditions of 0 ℃ for 30 minutes. The solution gradually changed from colorless to yellow and finally to brown-yellow. After the dropwise addition, reacting for 4 h in the environment to obtain yellowish turbid liquid, performing suction filtration, extraction, drying with anhydrous sodium sulfate, purifying by column chromatography, and vacuum dryingIntermediate 3 (14.3 g, 0.044 mol) was finally obtained in yellow after a series of treatments.
A500 mL dry round bottom flask was charged with potassium carbonate (50.0 g, 0.36 mol), intermediate 3 (14.3 g, 0.044 mol), potassium iodide KI 1.0g, and 6-chlorohexanol (12.0 g, 0.088 mol) and heated to 85 o C, adding 300 mL of tetrahydrofuran into the round-bottom flask, and stirring to completely dissolve the potassium carbonate. The round-bottom flask changed from milky to brown turbidity. After vigorous stirring for 4 h, cool to room temperature, extract with ethyl acetate, water, dry over anhydrous sodium sulfate, rotary evaporate the oil phase, then purify by column chromatography, then dry to give intermediate 4 (13.6 g, 0.032 mol).
Triethylamine (25 mL), methacryloyl chloride (5.0 g, 0.048 mol), intermediate 4 (13.6 g, 0.032 mol) was added to 300 mL of tetrahydrofuran solution and refluxed under argon. After 24 hours, 10wt% NH was added 4 20 mL of Cl aqueous solution. Then extracted with dichloromethane and the combined organic extracts washed with water and dried over anhydrous sodium sulfate. The crude product is then purified by flash chromatography and dried to give a yellow solidSAzobenzene monomer (12.8 g, 0.026 mol).
R-a step of synthesis of azobenzene monomer andSthe azobenzene monomer is the same except in stepR-octanol toSOctanol to yield 13.2 gR-an azobenzene monomer.
FIG. 1 is a nuclear magnetic diagram of the chiral azobenzene monomer, wherein a nuclear magnetic peak corresponds to the monomer, and no hetero peak exists, which indicates that the monomer is relatively pure.
The reaction process is schematically shown as follows:
Figure 781136DEST_PATH_IMAGE004
example 2: synthesis process of solvent-philic macromolecular chain transfer agent
The starting material methacrylic acid (5.16 g, 60.0 mmol), the small molecule chain transfer agent 4-cyano-4- (thiobenzoyl) pentanoic acid (0.28 g, 1.0 mmol), 4' -azo (4-cyanovaleric acid) (56.1 mg, 0.2 mmol) and the solvent ethanol (10.32 g) were added to a reaction vessel, the reaction temperature was controlled at 70 ℃, and the reaction was stirred for 5 hours. The reaction was stopped, then diluted with 2 mL of ethanol, settled in 500 mL of n-hexane for 3 times, then placed in a dialysis bag, dialyzed in 1000 mL of ethanol for three days, settled in 500 mL of n-hexane after the end of dialysis, and then completely dried. A solvophilic macromolecular chain transfer agent (PMAA macro-CTA) was obtained (4.32 g, 84% yield). Wherein the molar weight of the monomer and the molar ratio of the micromolecule chain transfer agent to the initiator are as follows: 60: 1: 0.2. FIG. 2 is a nuclear magnetic diagram and GPC outflow curve of the macromolecular chain transfer agent described above. Post-modification of the benzyl groups was performed for GPC testing, as is conventional. FIGS. 2B and 2C are post-modified nuclear magnetic maps and GPC outflow curves.
Example 3: general procedure for polymerization induced chiral self-assembly (PICSA)
The chiral monomer obtained in example 1 (A)SAn azobenzene monomer andRazobenzene monomer) (148.2 mg, 0.3 mmol), macromolecular chain transfer agent (93.3 mg, 0.02 mmol) obtained in example 2 and 4,4' -azo (4-cyanovaleric acid) (1.16 mg, 0.004 mmol) were added to a reaction vessel together with the solvent ethanol and water (2.17 g in total), deoxygenated with argon, 70 o And C, polymerizing for 15 hours to obtain the chiral supermolecule azobenzene assembly. Wherein the solid content of the reaction system is 10wt%, and the using amount of water is 4-20% of the volume of the ethanol; the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent to the 4' -azo (4-cyanovaleric acid) can be 12-18: 1: 0.2, products with different polymerization degrees can be obtained, for example, the molar ratio of the chiral azobenzene monomer to the macromolecular chain transfer agent is 15: 1, and the obtained chiral supramolecular azobenzene assembly is PMAA 51 -S 15 Or PMAA 51 -R 15 A block copolymer.
The chemical structural formula and the reaction of the chiral supramolecular azobenzene assembly are shown as follows:
Figure 223881DEST_PATH_IMAGE006
as shown in FIG. 3, at a water content of 20%, the polymerization time was 15 hours, and the A-graph nuclear magnetic tracking showed very little monomer residue, all of which were converted to polymer; the molecular weight-conversion curve in the B diagram shows that the conversion rate is extremely high and the molecular weight is close to quantitative.
FIG. 4 is PMAA 51 -S 15 And PMAA 51 -R 15 CD diagram of block copolymer assembly in water/ethanol mixed system andg CD figure (a). Wherein the water accounts for 4 percent (the water consumption is 0.1 mL), 10 percent and 20 percent of the total volume. The A diagram is CD and ultraviolet spectrum diagram of different water content, and the B diagram is CD and ultraviolet spectrum diagram of different water contentg CD Spectra. Whereing CD Is calculated as [ ellipticity/32,980]Absorbance. The volume of water is different, the CD of the block is fixed andg CD the values are different. PMAA 51 -S 15 And PMAA 51 -R 15 In the CD spectrogram and the ultraviolet spectrogram of the block copolymer assembly, the curves of upper and lower mirror images of the CD spectrogram indicate that supramolecular chirality is successfully constructed in the azobenzene block copolymer. PMAA 51 -S 15 And PMAA 51 -R 15 The photo-isomerism and reversible cycle chart test of the block copolymer assembly shows that the 365 nm ultraviolet light is used for prolonging the ultraviolet light irradiation time, PMAA 51 -S 15 And PMAA 51 -R 15 CD of (1) andg CD gradually decrease to disappearance, then after a heat (70 ℃) to cool (room temperature) treatment, CD andg CD and again recovered, and the disappearance-recovery process may cycle at least 5 times.
FIG. 5 is PMAA 51 -S 15 And PMAA 51 -R 15 TEM image of block copolymer assembly in water/ethanol mixed system. Wherein the percentage of water in the total volume is A graph and D graph 4%, B graph and E graph 10%, C graph and F graph 20%. The morphology of the fixed block is different when the volume of water is different. When the percentage of water is 4%, obtaining the long fibrous morphology of the A picture and the D picture; the fiber has a length of several micrometers and a width of 20-100 nanometers. However, when the molar ratio of chiral azobenzene monomer to macromolecular chain transfer agent is more than 20: 1, such as 25: 1, supramolecules are obtainedThe chiral azobenzene assembly is not in a helical fiber shape, such as a bubble shape, a sheet shape, and the like. If the ethanol in the preparation method is changed into N, N-dimethylformamide or tetrahydrofuran, the rest is not changed, an assembly cannot be obtained, the assembly is a dissolved polymer solution, and the fiber appearance cannot be generated.
FIG. 6 is PMAA 51 -S 15 And PMAA 51 -R 15 AFM images of block copolymer assemblies in a 4% water/ethanol mixed system. Wherein the percentage of water in the total volume is 4 percent, and long fibrous morphology is obtained; the AFM images are characterized by a helical fiber morphology.
In the product prepared by the invention, the supermolecule chirality combines the molecular chiral characteristics and the weak interaction force of supermolecule chemistry, and the chiral space structure formed by the non-covalent weak interaction force between chiral molecules or non-chiral molecules shows the chirality of the supermolecule ordered assembly body, but not the chirality of single molecules. In recent years, the rapid development of supramolecular science has led to the realization that optically active assemblies can be obtained by intermolecular non-covalent weak interactions in addition to intramolecular covalent bonds. Achiral molecules or chromophores can be induced to assemble into modules to form supramolecular aggregates with specific helical structures under the conditions of mechanical stirring, steric hindrance, circular polarized light and the like, so that chiral information can be amplified in a nonlinear mode; according to the invention, the azobenzene functional group is introduced as a photoresponse element so as to endow the material with remarkable optical properties. The polarity, shape and size of the azobenzene assembled unit can change rapidly under illumination, so that the ultraviolet visible spectrum (UV-vis) and Circular Dichroism (CD) spectrum of the azobenzene polymer can correspondingly show reversible changes. In the invention, along with the polymerization, the solubility of a polymer chain in a solution is reduced, the extension degree of a core chain segment in an assembly, the surface tension of a core and a solvent of the assembly and the repulsive force between a shell layer of the assembly and the soluble chain segment drive the amphiphilic block polymer to self-assemble into a nano assembly, and the assembly of the block copolymer with the fiber morphology can be quickly and conveniently constructed. Particularly, the invention introduces an azobenzene supermolecule structure into a polymer assembly, and constructs the supermolecule chiral non-liquid crystal polymer assembly containing azobenzene in situ through polymerization induction chiral self-assembly, thereby providing a strategy for effectively constructing the supermolecule chiral assembly of the azobenzene polymer with controllable and various shapes, and further functionalizing the material with controllable supermolecule chiral characteristics to expand the application range of the nano material containing azobenzene chiral.

Claims (8)

1. The preparation method of the chiral supramolecular azobenzene assembly is characterized by comprising the following steps of preparing a macromolecular chain transfer agent by taking a hydrophilic monomer and a micromolecular chain transfer agent as raw materials, mixing the chiral azobenzene monomer, the macromolecular chain transfer agent, a free radical initiator, an alcohol solvent and water, and carrying out polymerization reaction in an oxygen-free environment to obtain a supramolecular chiral azobenzene polymer; the chemical structural formula of the chiral azobenzene monomer is one of the following chemical structural formulas:
Figure 256248DEST_PATH_IMAGE001
Figure 973668DEST_PATH_IMAGE002
wherein a is 1-9 and b is 1-12.
2. The chiral supramolecular azobenzene assembly as claimed in claim 1, wherein alcohol solvent is any one of methanol, ethanol, propanol and butanol; the amount of the water is 0-90% of the total volume of the alcohol solvent and the water and does not include 0.
3. The chiral supramolecular azobenzene assembly as claimed in claim 1, wherein the polymerization reaction is carried out at 60-80 ℃ for 12-18 hours.
4. The chiral supramolecular azobenzene assembly as claimed in claim 1, wherein the molar ratio of chiral azobenzene monomer to macromolecular chain transfer agent is 12-18: 1.
5. The chiral supramolecular azobenzene assembly as claimed in claim 1, wherein methacryloyl chloride and intermediate product 4 are used as raw materials, and reflux reaction is carried out under inert gas to prepare chiral azobenzene monomer; the chemical structural formula of the intermediate product is one of the following chemical structural formulas:
Figure 821408DEST_PATH_IMAGE003
。
6. the chiral supramolecular azobenzene assembly as claimed in claim 5, wherein intermediate 1 is prepared from p-nitrophenol and chiral alcohol; the intermediate product 1 is subjected to amination and diazotization in sequence and then reacts with phenol to obtain an intermediate product 3; intermediate 3 is reacted with a halogen alcohol to provide intermediate 4.
7. The chiral supramolecular azobenzene assembly as claimed in claim 1, wherein said chiral supramolecular azobenzene assembly is fibrous.
8. Use of chiral supramolecular azobenzene assemblies as claimed in claim 1 for the preparation of chiral fibrillar polymers.
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